Abstract

Steep pedestal profiles of ion temperature (Ti) and toroidal rotation () are routinely observed in neutral beam injection (NBI)-heated KSTAR H-modeplasmas [W. H. Ko et al., Nucl. Fusion 55, 083013 (2015)]. In this work, we report a result of detailed analysis of pedestal characteristics. By analyzing a set of data with different experimental conditions, we show that Ti and pedestals are coupled to each other and correlation between them becomes stronger when NBI-torque is lower. This suggests the existence of intrinsic toroidaltorque in the pedestal. Based on a 1D transport analysis, we find that the prevalence of residual micro-turbulences is necessary to explain momentum transport in the pedestal. The estimated strength of intrinsic torque is shown to be comparable to that from a 2.7 MW NBI source. Finally, we show that non-diffusive momentum flux is indispensable to explain momentum transport in the pedestal, and a residual stress model fits the observed momentum flux reasonably.

This research was supported by the R&D Program through National Fusion Research Institute (NFRI) funded by the Ministry of Science, ICT and Future Planning of the Republic of Korea (NFRI-EN1541-2), and by the same Ministry under the ITER technology R&D programme (IN1504-2).